Page "D20 System" Paragraph 7

The rules for the d20 System are defined in the SRD ( currently version 3. 5 ), which may be copied freely or even sold.

Designed for fantasy-genre games in ( usually ) a pseudo-medieval setting, the SRD is drawn from the Dungeons & Dragons books Player's Handbook v3. 5, Expanded Psionics Handbook, Dungeon Master's Guide v3. 5, Monster Manual v3. 5, Deities and Demigods v3. 0, Unearthed Arcana, and Epic Level Handbook.

Information from these books not in the SRD include detailed descriptions, flavor-text, and material Wizards of the Coast considers Product Identity ( such as references to the Greyhawk campaign setting and information on mind flayers ).